Information processing method, information processing system and information processing apparatus

ABSTRACT

When information is transmitted among a plurality of devices connected through a network, an information opening data storage section for opening predetermined information is set to devices connected through the network, the information opening data storage section is formed in a descriptor format having a predetermined hierarchical structure, predetermined information is stored in a board  910  set in the descriptor format, the position at which the predetermined board  900  is stored is directly instructed by the highest-order descriptor  900  having the hierarchical structure, and information concerning a predetermined information is stored in information areas  921, 922, 931, 932  instructed when the hierarchical structure is retrieved from the highest-order descriptor  900.

TECHNICAL FIELD

The present invention relates to an information processing method, aninformation processing system and an information processing apparatusfor use with electronic devices such as AV devices connected to anetwork, for example, so that they can be controlled by aremote-controller. More particularly, this invention relates to aninformation processing method, an information processing system and aninformation processing apparatus suitably applied to the case in whichdevices can share information within the device by using a controlcommand such as a so-called AV/C command, for example.

BACKGROUND ART

Heretofore, there have been developed AV devices which are capable oftransmitting information with each other through a network using an IEEE1394 serial data bus prescribed by the IEEE (The Institute of Electricaland Electronics Engineers), for example. In this network, a user is ableto control the AV devices connected to the above network with each otherby using a predetermined command (AV/C Command Transaction Set:hereinafter abbreviated as an “AV/C command”) the details of the IEEE1394 system and the details of the AV/C command are described in theAV/C Digital Interface Command Set General Specification which is laidopen in the 1394 Trade Association.

As shown in FIG. 1,, when an IEEE 1394 serial data bus 51, (hereinafterreferred to as a “bus 51”) is used, video data received by an IRD(Integrated Receiver Decoder) 52, which is a digital satellite receiverfor receiving and decoding a digital satellite broadcasting, forexample, can be recorded by a DVCR (Digital Video Cassette Recorder) 53connected to the integrated receiver decoder via the bus 51. Further,video data can be recorded by these IRD 52 and DVCR 53 in a so-calledtimer-activated recording fashion under control of the AV/C command.

When video data is recorded by this apparatus in a timer-activatedrecording mode, the IRD 52 and the DVCR 53 are controlled by acontroller 54 provided within the IRD 52, for example. In this case, thesetting (channel, start time, etc.) of the timer-activated recording iseffected on the IRD 52. At the set start time, the controller 54 outputsa command to a digital tuner 55 provided within the IRD 52 so that thedigital tuner may select the set channel and that a video signal or thelike received by the digital tuner 85 from signals received at anantenna 56 is output to the bus 81.

At the same time, a recording start command is transmitted from thecontroller 54 through the bus 51 to a recorder 57 provided within theDVCR 53. Consequently, the recorder 57 obtains the video signal or thelike selected and received at the digital tuner 55 from the bus 51 andrecords the same on a recording medium such as a magnetic tape. Thetimer-activated recording is made in this manner. Further, the DVCR 53also includes a controller 58 to effect a control such as recording avideo signal or the like received at an analog tuner 59 incorporatedtherein by the recorder 57.

When the AV/C command, which controls the devices connected to thenetwork by the remote controller, shares information within the deviceswith other devices as described above, it has been customary thatinformation is shared by setting lists to the control target subunitsuch as a VCR subunit and a tuner subunit. However, according to theabove method, the contents of the shared information are limited tothose relating to the respective subunits. In accordance with thedevelopment of the future network system, there is a possibility thatthe contents of shared information will not be limited to those uniqueto the subunits but a demand of handling information of various contentswill increase.

On the other hand, the assignee of the present application haspreviously proposed an AV/C Bulletin Board Subunit (AV/C Bulletin BoardSubunit: hereinafter abbreviated as a “BBS”) as a space for sharinginformation independent of subunits (see the 1394 Trade AssociationBoard Subunit General Specification, Rev. 0.38). According to thissystem, the BBS can share arbitrary information thereby to controlarbitrary devices with each other.

However, in the previously-proposed BBS, a method required when boardsof a plurality of types should coexist and a list structure requiredwhen a plurality of boards of the same type should exist are notdefinite, and hence a variety of data cannot be stored efficiently.Accordingly, when data is read out from another device or data iswritten in another device, data should be processed after all data hadbeen read out from the BBS, for example, with the result that processingbecomes complicated. Therefore, there is an increasing demand ofefficiently writing and reading data by using the BBS.

DISCLOSURE OF INVENTION

In view of the aforesaid aspect, it is an object of the presentinvention to provide an information processing method, an informationprocessing system and an information processing apparatus in whichsatisfactory information processing, which cannot be made by aconventional information processing method, a conventional informationprocessing system and a conventional information processing apparatus,can be executed by using a BBS.

According to the first invention, there is provided an informationprocessing method of transmitting information among a plurality ofdevices connected through a network which is comprised of the steps ofsetting an information opening data storage section for openingpredetermined information to devices connected through the abovenetwork, forming the above information opening data storage section in adescriptor format having a predetermined hierarchical structure, storingthe above predetermined information in a board set in the abovedescriptor format, directly instructing the position at which the abovepredetermined information is stored in the predetermined board by ahighest-order descriptor of the above hierarchical structure and storinginformation concerning the above predetermined information in aninformation area instructed when the above hierarchical structure isretrieved from the above highest-order descriptor. With thisarrangement, another device connected through the network can easilyunderstand the position at which the predetermined information openedthrough the network is stored, and hence such information can easily beread out from the position at which it is stored. Moreover, anotherdevice can easily understand the position at which informationconcerning the predetermined information is stored.

According to the second invention, in the information processing methodaccording to the first invention, the information area includes an areain which information from other devices than the device in which thedescriptor is set can be written and an area in which the writing ofinformation from other devices is limited. With this arrangement, onlynecessary information can properly be protected from the writing ofinformation from other devices.

According to the third invention, in the information processing methodaccording to the second invention, when the above information writeenable area is set, information concerning a capacity in whichinformation can be written is added to the descriptor. With thisarrangement, other devices can judge a capacity in which information canbe written, and hence the writing of information can satisfactorily beexecuted within a prepared area.

According to the fourth invention, in the information processing methodaccording to the first invention, information stored in the board andinformation stored in the information area can be associated with eachother by adding IDs to respective information stored in the abovepredetermined board and by adding a common ID to respective informationstored in the above information area. With this arrangement, a user caneasily understand a correspondence between the information stored in theboard and the information stored in the information area with referenceto the IDs.

According to the fifth invention there is provided an informationprocessing, system for transmitting information among a plurality ofdevices connected through a network which is comprised of a first deviceconnected to the above network, the first device including aninformation opening data storage section for opening predeterminedinformation to devices connected through the above network and a controlsection for reading data or writing data stored in the above informationopening data storage section by receiving a predetermined commandthrough the above network and a second device connected to the abovenetwork including a control section for issuing a command whichinstructs the reading of data or the writing of data stored in the aboveinformation opening data storage section, in which data is stored in theinformation opening data storage section provided in the above firstdevice in a descriptor format having a predetermined hierarchicalstructure, the above predetermined information is stored in a board setin the descriptor format, the position at which the predeterminedinformation is stored in the above predetermined board is directlyinstructed by the highest-order descriptor having the hierarchicalstructure, and information concerning the above predeterminedinformation is stored in an information area instructed when the abovehierarchical structure is retrieved from the above highest-orderdescriptor. With this arrangement, the second device connected throughthe network can easily understand the position at which thepredetermined information opened through the network is stored, andhence there is obtained the system in which the information can easilybe read out from the first device. Moreover, the system can easilyunderstand the position at which the information concerning thepredetermined information is stored.

According to the sixth invention, in the information processing systemaccording to the fifth invention, an area in which information from thesecond device can be written and an area in which the writing ofinformation from the second device is limited are set to the informationarea within the information opening data storage section of the firstdevice. With this arrangement, a write protection from the second devicecan properly be effected only on necessary information.

According to the seventh invention, in the information processing systemaccording to the sixth invention, when an information write enable areais set as the above information area, a storage area of informationconcerning a capacity in which information can be written is added to adescriptor and the control section in the second device judges acapacity in which information can be written. With this arrangement,there is provided a system in which the second device can judge thecapacity in which information can be written and in which the writing ofinformation can satisfactorily be executed within a prepared area.

According to the eighth invention, in the information processing systemaccording to the fifth invention, IDs are added to respectiveinformation stored in the predetermined board within the informationopening data storage section of the above first device, a common ID isadded to respective information stored in the above information area andthe control section in the above second device can judge based on theIDs a correspondence between the information stored in the above boardand the information stored in the above information area. With thisarrangement, the second device side can easily understand based on theIDs a correspondence between the information stored in the board and theinformation stored in the information area.

According to the ninth invention, there is provided an informationprocessing apparatus for transmitting information to another deviceconnected through the network, which is comprised of an informationopening data storage section for opening predetermined information toanother device connected through the above network and a control sectionfor reading or writing data stored in the above information opening datastorage section by receiving a predetermined command through the abovenetwork, wherein data is stored in the above information opening datastorage section in the descriptor format having the hierarchicalstructure, the above predetermined information is stored in a board setin the above descriptor format, the position at which the predeterminedinformation is stored in the above predetermine board is directlyinstructed by the highest-order descriptor of the above hierarchicalstructure and information concerning the above predetermined informationis stored in an information area instructed when the above hierarchicalstructure is retrieved from the above highest-order descriptor. Withthis arrangement, another device connected through the network caneasily understand the position at which the predetermined informationopened through the network is stored, and hence such information caneasily be read out. Another device side which communicates with thisapparatus can easily understand the position at which informationconcerning the predetermined information is stored.

According to the tenth invention, in the information processingapparatus according to the ninth invention, an area in which informationfrom other devices can be written and an area in which the writing ofinformation from other devices is limited are set to the informationarea within the above information opening data storage section. Withthis arrangement, a write protection from another device connectedthrough the network can properly be effected only on necessaryinformation.

According to the eleventh invention, in the information processingapparatus according to the tenth invention, when an information writeenable area is set as the above information area, a storage area ofinformation concerning a capacity in which information can be written isadded to a descriptor. With this arrangement, another device connectedthrough the network can judge the capacity in which information can bewritten, and hence the writing of information can satisfactorily beexecuted within a prepared area.

According to the twelfth invention, in the information processingapparatus according to the ninth invention, IDs are added to respectiveinformation stored in a predetermined board within the above informationopening data storage section and a common ID is added to respectiveinformation stored in the above information area. With this arrangement,another device side connected through the network can easily understandbased on the IDs a correspondence between information stored in theboard and information stored in the information area.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing an arrangement of a conventional networkapparatus.

FIG. 2 is a diagram showing an arrangement of a network apparatusaccording to an embodiment of the present invention.

FIG. 3 is a block diagram showing an example of an arrangement of adigital satellite receiver.

FIG. 4 is a block diagram showing an example of an arrangement of avideo recording and reproducing apparatus.

FIG. 5 is an explanatory diagram showing an example of an IEEE 1394system frame structure.

FIG. 6 is an explanatory diagram showing an example of an address spacestructure of a CRS architecture.

FIG. 7 is an explanatory diagram showing examples of positions, namesand operations of major CRS.

FIG. 8 is an explanatory diagram showing an example of an arrangement ofa plug control register.

FIG. 9 is an explanatory diagram showing examples of arrangements ofoMPR, oPCR, iMPR, iPCR.

FIG. 10 is an explanatory diagram showing an example of a relationshipamong plugs, plug control registers and transmission channels.

FIG. 11 is an explanatory diagram showing an example of a data structurebased on a hierarchical structure of a descriptor.

FIG. 12 is an explanatory diagram showing an example of a data structureof a descriptor.

FIG. 13 is an explanatory diagram showing an example of a generation IDshown in FIG. 12.

FIG. 14 is an explanatory diagram showing an example of a list ID shownin FIG. 12.

FIG. 15 is an explanatory diagram showing an example of a stack model ofan AV/C command.

FIG. 16 is an explanatory diagram showing an example of a relationshipbetween commands and responses of the AV/C command

FIG. 17 is an explanatory diagram showing an example of a relationshipbetween commands and responses of the AV/C command more in detail.

FIG. 18 is an explanatory diagram showing an example of a data structureof an AV/C command.

FIG. 19 is an explanatory diagram showing concrete examples of AV/Ccommand.

FIG. 20 is an explanatory diagram showing concrete examples of commandsand response of the AC/C command.

FIG. 21 is an explanatory diagram showing an example of an arrangementof a BBS (bulletin board subunit).

FIG. 22 is an explanatory diagram showing an example of a data structureof a part of the BBS shown in FIG. 21.

FIG 23 is an explanatory diagram showing other example of a datastructure of a part of the BBS shown in FIG. 21.

FIG. 24 is a flowchart showing an example of processing executed when aboard shown by the BBS is readout.

FIG. 25 is a flowchart showing an example of processing executed when aboard list entry is read out.

FIG. 26 is a flow chart showing an example of processing executed whenan entry is read out from an information list.

FIG. 27 is a flowchart showing an example of processing executed when aninformation child list is read out.

FIG. 28 is an explanatory diagram showing examples of list types.

FIG. 29 is an explanatory diagram showing an example of a dataarrangement of an open command.

FIG. 30 is an explanatory diagram showing an example of a dataarrangement of a read command.

FIG. 31 is an explanatory diagram showing an example of a dataarrangement of a write command.

FIG. 32 is an explanatory diagram showing an example of a dataarrangement of a close command.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment according to the present invention will be described belowwith reference to FIGS. 2 to 32.

First, an example of an overall arrangement of an audio-visual systemaccording to this embodiment will be described with reference to FIG. 2.Specifically, as shown in FIG. 2, for example, an IRD 100 which is adigital satellite receiver for receiving and decoding a digitalsatellite broadcasting and a DVCR 200 which is a digital video recordingand reproducing apparatus are connected to a bus line 1 prescribed bythe IEEE 1394, for example. Although not shown, other devices may alsobe connected to the bus line 1.

The DVCR 200 includes a BBS (bulletin board subunit) 4 which functionsas a bulletin board for opening information to other devices. This BBS 4is set by storing corresponding data in a part of an area of a memoryconnected to a controller 10 within the DVCR 200, for example. Data canbe written in and read out from the BBS 4 under control of thecontroller 10 within the DVCR 200. The IRD 100 includes a BBS controller5 for reading and writing the BBS on the DVCR 200 side. When data isread and written under control of the IRD 100, there is used an AV/Cdescriptor mechanism prescribed by the AV/C command, for example. Thedetails of the AV/C command will be described later on.

When a timer-activated recording, for example, is executed, the IRD 100and the DVCR 200 are controlled by the BBS controller 5 in the IRD 100,for example. Accordingly, the setting (channel, start time, end time,etc.) of the timer-activated recording is effected on the BBS controller5 through the controller 6 of the IRD 100.

At the set start time, the BBS controller 5 outputs a command to adigital tuner 7 to select the set channel so that a video signal or thelike selected and received from signals captured at an antenna 8 by thedigital tuner 7 is outputted to the bus 1.

Simultaneously, a recording start command is transmitted from the BBScontroller 5 through the bus 1 to the BBS 4 within the DVCR 200.Consequently, a command is outputted from the BBS 4 within the DVCR 200to a recorder 9 and a video signal or the like channel-selected andreceived by the digital tuner 7 is obtained from the bus 1, therebybeing recorded on a recording medium such as a magnetic tape. Thetimer-activated recording is made in this manner. Further, the DVCR 200also includes a controller 10 to control such operation as to record thevideo signal or the like received at the incorporated analog tuner 11,for example by the recorder 9. While the BBS controller 5 and thecontroller 6 are formed independently as shown in FIG. 2, in actualpractice, a part of a CPU comprising the controller 6, for example, isset so as to function as the BBS controller 5.

FIG. 3 is a diagram showing an arrangement of the IRD 100. Broadcastwaves from a satellite are received at the antenna 8, inputted to aterminal 100 a and supplied to a tuner 101 serving as a programselecting means provided within the IRD 100. The IRD 100 is arrangedsuch that its respective circuits are operated under control of acentral processing unit (CPU) 111. A signal of a predetermined channelis obtained from the tuner 101. The received signal obtained by thetuner 101 is supplied to a descramble circuit 102.

Based on encrypted key information of a subscribed channel stored in anIC card (not shown) inserted into the body of the IRD 100, thedescramble circuit 102 extracts only multiplexed data of a subscribedchannel (or channel which is not yet encrypted) from received data andsupplies the multiplexed data thus extracted to a demultiplexer 103.

The demultiplexer 103 rearranges the multiplexed data supplied theretoat every channel, extracts only data of the channel designated by auser, transmits a video stream comprising packets of video portion to anMPEG video decoder 104 and also transmits an overlap stream comprisingpackets of audio portion to an MPEG audio decoder 109.

The MPEG decoder 104 decodes the video stream to restore video datawhich is not yet compression-coded and transmits such video data throughan adder 105 to an NTSC encoder 106. The NTSC encoder 106 encodes thevideo data to provide NTSC system luminance signal and color differencesignals and transmits the same to a digital-to-analog converter 107 asNTSC system video data. The digital-to-analog converter 107 converts theNTSC data into an analog video signal and supplies the analog videosignal to a connected receiver (not shown).

The IRD 100 according to this embodiment includes a GUI data generatingsection 108 which generates various kinds of display video data for agraphical user interface (GUI) under control of the CPU 111. The GUIvideo data (display data) generated by this GUI data generating section108 is supplied to the adder 105, in which it is superimposed upon thevideo data outputted from the MPEG video decoder 104 and thereby a GUIpicture is superimposed upon a broadcast picture.

The MPEG audio decoder 109 decodes an audio stream to restore PCM audiodata which is not yet compression-coded and transmits the same to adigital-to-analog converter 110.

The digital-to-analog converter 110 converts the PCM audio data into ananalog signal to provide a left channel audio signal and a right channelaudio signal, and outputs the same through speakers (not shown) of aconnected audio reproducing system as sounds.

The IRD 100 according to this embodiment can supply the video stream andthe audio stream extracted by the demultiplexer 103 to an IEEE 1394interface section 112 from which they can be transmitted to the IEEE1394 system bus line 1 connected to the interface section 112. Thereceived video stream and audio stream are transmitted in theisochronous transfer mode. Further, while the GUI video data is beinggenerated by the GUI data generating section 108, the above video datais supplied through the CPU 111 to the interface section 112 so that theGUI video data can be transmitted from the interface section 112 to thebus line 1.

A RAM 113 for work area and a RAM 114 are connected to the CPU 111, andcontrol processing is executed by using these memories. Operationcommands from an operating panel 115 and a remote control signal from aninfrared-ray light-receiving section 116 are supplied to the CPU 111which can therefore be driven based on a variety of operation. The CPU111 can judge commands and responses transmitted from the bus line 1side to the interface section 112.

FIG. 4 is a block diagram showing an example of an arrangement of theDVCR 200.

In the arrangement of the recording system, digital broadcasting dataobtained when a tuner 201 incorporated in the DVCR 200 received data ofa predetermined channel is supplied to an MPEG (Moving Picture ExpertsGroup) encoder 202, in which it is encoded to provide video data andaudio data suitable for recording, e.g., MPEG2 system video data andaudio data. If received broadcasting data is MPEG2 system data, thensuch received broadcasting data need not be processed by the encoder202.

The data encoded by the MPEG encoder 202 is supplied to a recording andreproducing section 203, in which it is processed for recording. Therecording data thus processed is supplied to a recording head providedwithin a rotary head drum 204 and thereby recorded on a magnetic tapeprovided within a tape cassette 205.

After an analog video signal and an analog audio signal inputted fromthe outside had been converted into digital data by an analog-to-digitalconverter 206, they are supplied to the MPEG encoder 202, in which theyare encoded to provide MPEG2 system video data and audio data andsupplied to the recording and reproducing section 203 and therebyprocessed for recording. The recording data thus processed is suppliedto the recording head provided within the rotary head drum 204 andthereby recorded on a magnetic tape provided within the tape cassette205.

In the arrangement of the reproducing system, a signal obtained when themagnetic tape within the tape cassette 205 is reproduced by the rotaryhead drum 204 is supplied to the recording and reproducing section 203,in which it is processed for reproduction to provide video data andaudio data. The video data and the audio data are supplied to an MPEGdecoder 207, in which they are decoded from MPEG system video data andaudio data, for example. The decoded data are supplied to adigital-to-analog converter 208, in which they are converted into ananalog video signal and an analog audio signal and then outputted to theoutside.

The DVCR 200 includes an interface section 209 for the connection to theIEEE 1394 system bus. Video data and audio data obtained at thisinterface section 209 from the IEEE 1394 system bus side are supplied tothe recording and reproducing section 203 and thereby recorded on themagnetic tape provided within the tape cassette 205. Video data andaudio data reproduced from the magnetic tape provided within the tapecassette 205 are supplied from the recording and reproducing section 203to the interface section 209 from which they can be transmitted to theIEEE 1394 system bus side.

When video data and audio data are transmitted through the interfacesection 209, if the system in which video data and audio data arerecorded on a medium (magnetic tape) by the DVCR 200 and the system ofdata transmitted over the IEEE 1394 system bus differ from each other,then the system may be converted by circuits provided within the DVCR200.

The recording processing and the reproducing processing by the DVCR 200and the transmission processing through the interface section 209 areexecuted under control of the central processing unit (CPU) 210. Thememory 211 which is the RAM for work area is connected to the CPU 210.Operation information from an operating panel 212 and controlinformation received by an infrared-ray light-receiving section 213 fromthe remote control apparatus are supplied to the CPU 210 which cancontrol operation corresponding to the operation information and thecontrol information. Further, when the interface section 209 receivescontrol data such as an AV/C command, which is described later, throughthe IEEE 1394 system bus, the above data is supplied to the CPU 210, andhence the CPU 210 can control corresponding operation.

Next, the manner in which data is transmitted through the IEEE 1394system bus to which the respective devices 100, 200 are connected willbe described.

FIG. 5 is a diagram showing a data transmission cycle structure of adevice connected via the IEEE 1394. According to the IEEE 1394, data isdivided into packets and transmitted in a time-division manner based ona cycle of a duration of 125 (S. This cycle is created by a cycle startsignal supplied from a node having a cycle master function (any deviceconnected to the bus). An isochronous packet secures a band necessaryfor transmission (referred to as a “band” although it is a time unit)from the start of all cycles. Accordingly, in the isochronoustransmission, the transmission of data within a constant time can beassured. However, if a transmission error occurs, then data will be lostbecause this data transmission cycle structure has no mechanism forprotecting data from the transmission error. In the asynchronoustransmission in which a node, which secures a bus as a result ofarbitration in a time which is not used in the isochronous transmissionof each cycle, transmits the asynchronous packet, although a reliabletransmission is assured by using acknowledge and retry, a transmissiontiming cannot be made constant.

When a predetermined node transfers data in the isochronous transfermode, such node has to be corresponding to the isochronous function. Atleast one of the nodes corresponding to the isochronous function has tohave a cycle master function. Further, at least one of the nodesconnected to the IEEE 1394 serial bus has to have an isochronousresource manager function.

The IEEE 1394 is based on a CSR (Control & Status Register) architecturehaving 64-bit address space prescribed by the ISO/IEC 13213. FIG. 6 is adiagram to which reference will be made in explaining a structure of aCSR architecture address space. High-order 16 bits represent a node IDindicative of a node on each IEEE 1394, and remaining 48 bits are usedto designate an address space given to each node. The high-order 16 bitsare separated into 10 bits of a bus ID and 6 bits of a physical ID (nodeID in a narrow sense). Values in which all bits go to 1 are for use as aspecial purpose, and hence 1023 buses and 63 nodes can be designated.

A space prescribed by high-order 20 bits of 256-terabyte address spaceprescribed by low-order 48 bits is separated into an initial registerspace for use as a register unique to 2048-byte CSR, a register uniqueto the IEEE 1394, or the like, a private space and an initial memoryspace. A space prescribed by low-order 28 bits are for use as aconfiguration ROM (Configuration read only memory), an initial unitspace for use unique to a node and plug control register (PCRs) if aspace prescribed by its high-order 20 bits is the initial registerspace.

FIG. 7 is a diagram to which reference will be made in explaining offsetaddresses, names and operation of major CSRs. The offset in FIG. 7indicates an offset address from FFFFF0000000h (numerals with hrepresent a hexadecimal notation) from which the initial resister spacebegins. A bandwidth available register (Bandwidth Available Register)having an offset 220h represents a band which can be allocated to theisochronous communication, and only a value of node which is beingoperated as an isochronous resource manager is made effective.Specifically, although each node includes the CSR shown in FIG. 6, onlythe bandwidth available register of the isochronous resource manager ismade effective. In other words, only the isochronous resource managerincludes the bandwidth available register substantially. The bandwidthavailable register preserves a maximum value when the band is notallocated to the isochronous communication and its value decreases eachtime the band is allocated to the isochronous communication.

A channel available register of offsets 224h to 228h has bitsrespectively corresponding to channel numbers from channel 0 to channel63. If the bit is 0, then this shows that the corresponding channel isalready allocated. Only the channel available register of the node whichis being operated as the isochronous resource manager is effective.

Referring back to FIG. 6, a configuration ROM based on a general ROM(read only memory) format is located at addresses 200h to 400h withinthe initial register space. Bus info block, root directory and unitdirectory are located at the configuration ROM. An ID number indicativeof vender of devices is stored in a company ID within the bus infoblock. A unique ID unique to the device is stored in a chip ID.

In order to control input and output of the device through theinterface, the node includes a PCR (Plug Control Register), prescribedby the IEC 1833, at addresses 900h to 9FFh within the initial unit spaceshown in FIG. 6. This is a substantiation of a concept of a plug inorder to form a signal channel similar to an analog interface from alogical standpoint. FIG. 8 is a diagram to which reference will be madein explaining the arrangement of the PCR. The PCR includes an OPCR(output Plug Control Register) expressing an output plug and an iPCR(input Plug Control Register) expressing an input plug. The PCR alsoincludes registers oMPR (output Master Plug Register) and iMPR (inputMaster Plug Register) indicating information of the output plug or theinput plug proper to each device. Each device cannot include a pluralityof oMPRS and iMPRs but can include a plurality of oPCRs and iPCRscorresponding to individual plugs depending upon a device capability.The PCR shown in FIG. 8 includes 31 oPCRs and iPCRs. The flow ofisochronous data can be controlled by operating registers correspondingto these plugs.

FIG. 9 is a diagram showing arrangements of the oMPR, the oPCR, the iMPRand the iPCR. FIG. 9A shows the arrangement of the oMPR, FIG. 9B showsthe arrangement of the oPCR, FIG. 9C shows the arrangement of the iMPRand FIG. 9D shows the arrangement of the iPCR, respectively. A codeindicative of a maximum transfer speed of isochronous data that thedevice can transmit or receive is stored in the 2-bit data ratecapability on the MSB side of the oMPR and the iMPR. A broadcast channelbase of the oMPR prescribes the channel number for use with thebroadcast output.

The number of the output plugs of the device, i.e., the value indicativeof the number of the oPCRs is stored in the number of the output plugsof 5 bits on the LSB side of the oMPR. The number of the input plugs ofthe device, i.e., the value indicative of the number of the iPCRs isstored in the number of the input plugs of 5 bits on the LSB side of theiMPR. A main extended field and an auxiliary extended field are theareas defined for future extension.

An on-line on the MSB of the oPCR and the iPCR shows the state in whichthe plug is in use. Specifically, if its value is 1, then it isindicated that the plug is on-line. If its value is 0, then it isindicated that the plug is off-line. A value of the broadcast connectioncounter of the oPCR and the iPCR expresses whether the broadcastconnection exists (1) or not (0). A value that a point-to-pointconnection counter having a 6-bit width of the oPCR and the iPCRexpresses the number of point-to-point connection of the plug. Thepoint-to-point connection (so-called p-to-p connection) is a connectionused to transmit data among one specified node and another specifiednode.

A value of a channel number having a 6-bit width of the oPCR and theiPCR expresses the isochronous channel number to which the plug isconnected. A value of a data rate having a 2-bit width of the oPCRexpresses a real transmission speed of packets of the isochronous dataoutputted from the plug. A code stored in an overhead ID having a 4-bitwidth of the oPCR expresses a band width of the overhead of theisochronous communication. A value of a payload having a 10-bit width ofthe oPCR expresses a maximum value of data contained in the isochronouspackets that the plug can handle.

FIG. 10 is a diagram showing a relationship among the plug, the plugcontrol register and the isochronous channel. Devices connected to theIEEE 1394 system bus are shown as AV devices 71 to 73. Isochronous datawhose channel was designated by the oPCR [1] of the oPCR [0] to the oPCR[2] in which the transmission speed and the number of the oPCRs areprescribed by the oMPR of the AV device 73 is transmitted to the channel#1 of the IEEE 1394 serial bus. Based on the transmission speed of theinputted channel #1 and the iPCR [0] of the iPCR, [0] and the iPCR [1]inwhich the transmission speed and the number of the iPCRS are prescribedby the iMPR of the AV device 71, the AV device 71 reads the isochronousdata transmitted to the channel #1 of the IEEE 1394 serial bus. In alike manner, the AV device 72 transmits isochronous data to the channel#2 designated by the oPCR [0], and the AV device 71 reads theisochronous data from the channel #2 designated by the iPCR [1].

In this manner, data is transmitted among the devices connected by theIEEE 1394 serial bus. The system according to this embodiment cancontrol respective devices and judge the states by using the AV/Ccommand set prescribed as commands for controlling the devices connectedthrough the IEEE 1394 serial bus. The AV/C command set will be describednext.

First, a data structure of a subunit identifier descriptor in the AV/Ccommand set used by the system according to this embodiment will bedescribed with reference to FIGS. 11 to 14. FIG. 11 shows the datastructure of the subunit identifier descriptor. As shown in FIG. 11,data is formed by lists of a hierarchical structure of the subunitidentifier descriptor. A list expresses a receivable channel if it is atuner and expresses a recorded number if it is a disc. The list at theuppermost position of the hierarchical structure is called a root list,and a list 0 becomes a root for low-order lists. Other lists also becomeroot lists. There exist root lists as many as the objects. The objectexpresses each channel in the digital broadcasting or the like if the AVdevice connected to the bus is the tuner. All lists in one hierarchyshare common information.

FIG 12 shows a format of the general subunit descriptor. The subunitdescriptor describes therein attribute information concerning functionsas contents. A descriptor length field does not contain a value of itsown field. A generation ID indicates a version of the AV/C command set,and its value is “00h” (h expresses the hexadecimal notation), forexample. “00h” means that the data structure and the command are basedon the version 3.0 of the AV/C general specification as shown in FIG.13, for example. As shown in FIG. 13, all values excepting “00h” arereserved for future specification.

A size of list ID expresses the number of bytes of the list ID. A sizeof object ID expresses the number of bytes of the object ID. A size ofobject position expresses the position (number of bytes) in the listwhich is looked up upon control. The number of root object listexpresses the number of the root object lists. A root object list IDshows an ID used to identify the highest-order root object list in therespective independent hierarchies.

A subunit dependent length expresses the number of bytes of a followingsubunit dependent data field (subunit dependent information) field. Thesubunit dependent data field is the field indicating function dependentinformation. A manufacturer dependent data length (manufacturerdependent length) indicates the number of bytes of a followingmanufacturer dependent data (manufacturer dependent information) field.Manufacturer dependent data is a field indicating specificationinformation of a vender (manufacturer). When the descriptor does notcontain the manufacturer dependent data, this field does not exist.

FIG. 14 shows a range in which the list ID shown in FIG. 12 isallocated. As shown in FIG. 14, “0000h” to “0FFFh” and “4000h” to“FFFFh” are reserved as allocation ranges for future specification.“1000h to 3FFFh” and “10000h to maximum value of list ID” are preparedin order to identify dependent information of function types.

Next, the AV/C command set used in the system according to thisembodiment will be described with reference to FIGS. 15 to 20. FIG. 15shows a stack model of the AV/C command set. As shown in FIG. 15, aphysical layer 81, a link layer 82, a transaction layer 83 and a serialbus management 84 are based on the IEEE 1394. An FCP (Function ControlProtocol) 85 is based on the IEC 61883. An AV/C command set 86 is basedon the 1394 TA specification.

FIG. 16 is a diagram used to explain commands and responses of the FCP85 shown in FIG. 15. The FCP is the protocol used to control devices(nodes) on the IEEE 1394 system bus. As shown in FIG. 16, a control sideassumes a controller and a controller side assumes a target. Thetransmission or the response of the command in the FCP is executedbetween the nodes by using a write transaction of the asynchronouscommunication of the IEEE 1394 asynchronous communication. The targetwhich received data returns acknowledge to the controller in order toconfirm the reception.

FIG. 17 is a diagram to which reference will be made in explaining therelationship between the command and the response in the FCP shown inFIG. 16 more in detail. Nodes A and B are connected together via theIEEE 1394 bus. The node A is the controller and the node B is thetarget. Both of the nodes A and B include 512-byte command register andresponse register. As shown in FIG. 17, the controller transmits acommand by writing a command message in a command register 93 of thetarget. Conversely, the target transmits a response by writing aresponse message in a response register 92 of the controller. Controlinformation is transmitted and received for the above two messages. Thetypes of the command set transmitted by the FCP are written in a CTS inthe data field of FIG. 18 which will be described later on.

FIG. 18 shows a data structure of packets transmitted in theasynchronous transfer mode of the AV/C command. The AV/C command set isthe command set used to control the AV devices,,and CTS (command setID)=“0000”. An AV/C command frame and a response frame are transmittedand received between the nodes by using the above FCP. In order toprevent a load from being imposed upon the bus and the AV devices, theresponse for the command should be transmitted within 100 ms. As shownin FIG. 18, data of asynchronous packet is comprised of 32 bits (=1quadlet) in the horizontal direction. In the figure, the upper stageshows a packet header portion and the lower stage in the figure shows adata block. A destination (destination ID) shows a destination.

The CTS shows a command set ID and CTS=“0000” in the AV/C command set. AC type/response field shows a command function type when the packet isthe command, and shows a processed result of command when the packet isthe response. Roughly classified, there are four types of commandswherein (1) a command CONTROL for, controlling the functions from theoutside, (2) a command STATUS for inquiring the status from the outside,(3) a command for inquiring the existence of the support of the controlcommand from the outside GENERAL INQUIRY (existence of support ofopcode) and SPECIFIC INQUIRY (existence of support of opcode andoperands) and (4) a command NOTIFY for notifying the change of thestatus to the outside.

Response messages are returned in response to the type of the command.Response messages for CONTROL command are NOT IMPLEMENTED, ACCEPTED,REJECTED and INTERIM. Response messages for STATUS command are NOTIMPLEMENTED, REJECTED, IN TRANSITION and STABLE. Response messages forthe command GENERAL INQUIRY and SPECIFIC INQUIRY for inquiring theexistence of the support of the command from the outside are IMPLEMENTEDand NOT IMPLEMENTED. Response messages for the command NOTIFY fornotifying the change of the status to the outside are NOT IMPLEMENTED,REJECTED, INTERIM and CHANGED.

The subunit type is provided in order to specify functions within thedevice, and tape recorder/player, tuner and so on are allocated to thesubunit type. In addition to the functions corresponding to the devices,the subunit type is also allocated to the BBS (bulletin board subunit)which opens information to other devices. In order to discriminate aplurality of subunits of the same type, the addressing is executed byusing the subunit ID (subunit ID) as a discrimination number. An opcodeexpresses a command, and an operand expresses a parameter of a command.There are prepared fields (additional operands) which should be added ifnecessary. Null data and the like are added to the operand if necessary.A data CRC (Cyclic Reduncy Check) is used to check errors when data istransmitted.

FIG. 19 shows examples of the AV/C command in concrete. The left-handside in FIG. 19 shows examples of the c type/response messages inconcrete. In the figure, the upper stage expresses command messages, andthe lower stage in the figure expresses response messages. CONTROL isallocated to “0000”, STATUS is allocated to “0001”, SPECIFIC INQUIRY isallocated to “0010”, NOTIFY is allocated to “0011”, and GENERAL INQUIRYis allocated to “0100”, “0101 to 0111” are reserved for futurespecification. NOT IMPLEMENTED is allocated to “1000”, ACCEPTED isallocated to “1001”, REJECTED is allocated to “1010”, IN TRANSITION isallocated to “1011”, IMPLEMENTED/STABLE is allocated to “1100”, CHANGEDis allocated to “1101” and INTERIM is allocated to “1111”, “1110” isreserved for future specification.

The center portion in FIG. 19 shows examples of subunit types inconcrete. A video monitor is allocated to “00000”, a discrecorder/player is allocated to “00011”, a tape recorder/player isallocated to “00100”, a tuner is allocated to “00101”, a video camera isallocated to “00111”, a BBS is allocated to “01010, a vender uniquesubunit type (Vender unique) is allocated to “11100” and a specificsubunit type (subunit type extended to next byte) is allocated to“11110”. While a unit is allocated to “11111”, this is used when it istransmitted to the device itself and might be the on/off of the powersupply, for example.

The right-hand side of FIG. 19 shows examples of opecode (operationcode: opcode) in concrete. A table of opecodes exists at every subunittype. The right-hand side shows opecodes obtained when the subunit typeis the tape recorder/player. Operands are defined for every opecode. Avender dependent value is allocated to “00h”, a search mode is allocatedto “50h”, a time code is allocated to “51h”, an ATN is allocated to“52h”, an open memory is allocated to “60h”, a memory read is allocatedto “61h”, a memory write is allocated to “62h”, a load is allocated to“C1h”, a recording is allocated to “C2h”, a reproduction is allocated to“C3h” and a rewinding is allocated to “C4h”.

FIG. 20 shows examples of the AV/C command and response in concrete. Forexample , when a user instructs a playback to a reproducing deviceserving as a target (consumer), the controller transmits the commandshown in FIG. 20A to the target. Since this command uses the AV/Ccommand set, CTS=“0000”. Since the ctype uses the command CONTROL forcontrolling the device from the outside, c type=“0000” (see FIG. 19).Since the subunit type is the tape recorder/player, the subunittype=“00100” (see FIG. 19).; Identification code id shows the case ofID0 and hence id=000. The opecode is allocated to “C3h” which means thereproduction (see FIG. 19). The operand is allocated to “75h” whichmeans the forward direction (FORWARD). When data is reproduced, thetarget transmits the response message shown in FIG. 20B to thecontroller. Since the response message “ACCEPTED” enters the responsemessage, response=“1001” (see FIG. 19). Portions other than the responseare the same as those of FIG. 20A and therefore need not be described.

Next, the arrangement of the BBS (bulletin board-subunit) which is thesubunit for opening information to other devices prepared in the aboveAV/C command set and processing using such BBS will be described withreference to FIG. 21 and the following sheets of drawings.

In this embodiment, the BBS is comprised of descriptors having ahierarchical structure shown in FIG. 21, for example. Specifically, aBBSID (Bulletin Board Subunit Identifier Descriptor) 900 which shows adata structure of BBS is provided at the highest-order class.Descriptors and positions of boards in actual practice are instructed byroot list IDs, shown by the BBSID 900. This BBSID is prescribed by [1394Trade Association Board Subunit General Specification] which is thespecification of bulletin board and presents lists which areindispensable for the subunits of the bulletin board. The controllershould read this list when it accesses the BBS for the first time.

Board lists and information lists are disposed at the classes under theBBSID 900. For the board list and the information list, there are settwo kinds of the read-only board list and information list and the writeenable board list and information list, respectively. Specifically, asshown in FIG. 28 which shows a list of list types, a list type having avalue 80 is set to a read-only board list, and a list type having avalue 81 is set to a write enable board list. A list type having a value82 is set to a read-only information list, and a list type having avalue 83 is set to a write enable information list The read-only list issuch one in which information cannot be written by an instruction from acontroller of an external device different from a device including a BBSand in which information can be written by an instruction from aninternal controller of a device including a BBS.

The BBSID 900 stores therein fundamental information used to read andwrite the lists provided within the BBS. To be concrete, as shown inFIG. 22, predetermined information such as size are provided in thefirst list of the BBSID 900. Further, these information are followed byroot list IDs. These root list IDs are served as pointers to the boardlists directly connected to the respective BBS. One value is assigned toeach of these root list IDs at every board type.

Specifically, as shown by a list ID assignment 901 shown in FIG. 22, forexample, this root list ID is defined by values ranging from 0000 toFFFF in a hexadecimal notation. Of these values, values from 1000 to1FFF are used to define the root list ID. Values ranging from 2000 to3FFF of the root list ID are used as a free space for a default list.Further, values ranging from 0000 to 1FFF of the root list ID and valuesranging from 4FFF to FFFF are reserved. The values of these root listIDs are opened by the specification and the like.

In the above BBSID 900, there are provided a plurality of root list IDsdepending upon board types. In the example of FIG. 22, there areprovided three kinds of BBS of types A to C. Further, these root listIDs are followed by BBS unique information, vender unique informationand the like.

The root list ID of the type A becomes a pointer to a resource scheduleboard (RSB) 910. Information concerning the concrete setting of atimer-activated recording (channel, start time, etc.) are written inthis resource schedule board 910. Object IDs are individually set to theinformation written in the resource schedule board 910 and informationof the object IDs are written in the resource schedule board 910. Thisobject ID is commonly used so long as it is information concerning thesame timer-activated recording. Specifically, in the case of thisembodiment, although only fundamental information concerning thetimer-activated recording is written in the resource schedule board 910and information accompanying with each timer-activated recording iswritten in information list descriptors 921, 922, 931, 932 which will bedescribed later on, fundamental information and information accompanyingwith each timer-activated recording are associated with each other bysetting the same object IDs as the object IDs of respective, itemswithin the resource schedule board 910 to respective items within theinformation list descriptor.

Board list descriptors 920, 930 shown in FIG. 22 are retrieved by theroot list IDs of the types B, C of the BBSID 900.

The board list descriptor 920 shows a write enable board listdescriptor. The write enable board list descriptor shows thatinformation can be written therein from another device connected via thebus line 1. It is needless to say that information can be written inthis write enable board list descriptor by its own controller. The boardlist descriptor 920 shows a data length of list first and then showsthat the list type is the write enable board list. Further, this boardlist descriptor shows the attributes of whether or not it has an objectID and a capacity of board that can be formed as list information.Furthermore, this board list descriptor shows the number of preparedboard entries.

The board list descriptor is followed by information concerningrespective boards specifically, assuming that the number of the boardentries is in, for example, then there exist board entries from 0 entrytype to n-1 entry type. As 0 entry type information 920 a, it isindicated that the entry type is the board and it is determined whetheror not the board has a child list as an attribute. If the board has thechild list, then there is provided a child list ID. This child list IDinstructs the position of a descriptor (#B-1) 921 serving as a childlist. As entry information, there are provided a board type and a fieldin which information concerning the details of the board type arewritten. Further, there are provided such lists as many as the boards.For example, there is similarly provided information 920 b of 1 entrytype, and the position of descriptor. (#B-n) 922 is instructed by achild list ID of such information.

The board list descriptor 930 shown in FIG. 22 shows a read only boardlist descriptor. In this case, first, the list type shows that the boardis the read only board. The read only board shows the board in whichinformation cannot be written by another device connected through thebus line 1. Information can be written in the read only board by its owncontroller. Further, the attribute shows whether or not this board listdescriptor has, an object ID, a capacity of a board that can be formedas list information and the number of board entries.

These are followed by information concerning respective boards.Specifically, 0 entry type information 930 a, for example, shows thatthe entry type is the board and whether or not the attribute has a childlist. If the attribute has the child list, then there is provided achild list ID. The position of a descriptor 931 serving as the childlist is instructed by this child list ID. Moreover, as the entryinformation, there are provided a board type and a field in whichinformation concerning details of the board type is written. Further,there are provided lists as many as the number of boards .

In an information list descriptor (#B-1) 921 shown in FIG. 23, first,the list type shows that this list is a write enable information list,for example. Further, the attribute shows whether or not thisinformation list descriptor has an object ID, a capacity that can beformed as a list specification and information of the number of entries.

These are followed by information concerning respective information.Specifically, 0 entry type information 921 a shows that this informationis preset information and whether or not this information has a childlist as an attribute. If this information does not have a child list,then there is not provided a field of a child list ID. Then, there areprovided a an object ID and preset information, for example. Further,there are provided lists as many as the number of information. Anotherinformation list descriptor (#B-n) 922 of the same class has a similardata arrangement and need not be described in detail.

In an information list descriptor (#C-1) 931 which is a child list ofthe board list descriptor 930, the position is instructed by the childlist ID of the board list descriptor 930. This information listdescriptor #C-1 shows that this descriptor further includes a childlist.

In the information list descriptors (#C-1) 931, first, a list type showsthat information is read only information. An attribute shows whether ornot information includes an object ID and also shows list information, acapacity in which information can be formed as a list and the number ofentries.

The above items are followed by information 931 a concerning eachinformation. Specifically, 0 entry type shows that information is Å¢ Å¢A information and an attribute shows whether or not information includesa child list. If information includes the child list, then there are,provided a child list ID, an object ID and an information entry.Further, there are provided lists as many as the number of information.

An information child list descriptor (#C-1-1) 932 which is located atthe class under such descriptor is retrieved by the child list IDprovided in this descriptor. In this descriptor (#C-1-1) 932, first, alist type shows that information is a read only board and an attributeshows whether or not information includes an object ID.

Further, list information, a capacity in which information can be formedas a board and the number of entries are shown. As informationconcerning each information, e.g., ask 0 entry type information 932 a,the attribute shows whether or not information includes a child list.There is also provided an information entry specific. There are providedthe above lists as many as the number of entries.

According to the bulletin board subunit thus arranged, since the ID ofthe root list ID is assigned to each board type as described above, thecontroller can read the root list ID from the BBSID and can confirm bycomparing it with a target board type whether or not the target boardtype exists within a target subunit.

Each root list ID shows the starting list comprising the board or theboard list comprised of a plurality of boards of the same type. Thecontents of the board and the board list are as follows. The board iscomprised of more that one information list descriptor The board listdescriptor comprised of a plurality of boards of the same type shows apointer of a starting information list descriptor of each board.

As the board list descriptor comprised of a plurality of board types,there are available two types of a write enable board list descriptorand a read only board list descriptor. These types can be discriminatedfrom each other by a list type. The controller can generate, accordingto the write enable board list, the boards of the same type in a remotecontrol fashion. Having detected that the list type is of the writeenable list type, the controller issues a write executing command towrite data and can set necessary data within the descriptor .

Further, these data can be accessed by using an AV/C OPEN/READ/WHITEDescriptor command prescribed by the AV/C command, for example.

Specifically, when the descriptor within the BBS is accessed, first, acorresponding descriptor is set in a read or write state by transmittingan OPEN DESCRIPTOR command having an arrangement shown in FIG. 29. Inthis open descriptor command, as shown in FIG. 29, for example, valuescorresponding to the open descriptor commands are located to the opecodefield, a value of the type of descriptor to be opened is located at thefield of the operand [0], a value of list ID to be opened is located atthe fields of the operands [1], [2] and a value of subfunction islocated at the field of the operand [3]. When the descriptor is openedfor writing, for example, a value of write open is located assubfunction. When the descriptor is opened for reading, a value of readopen is located. Fields following the filed of the operand [4] arereserved.

When data is read out from the descriptor which can be set to theaccessible state by the open descriptor command shown in FIG. 29,necessary data is read out from the descriptor by transmitting a readcommand. FIG. 30 shows an arrangement of this read command. Thearrangement of this read command will be described. A valuecorresponding to the read descriptor command is located at the field ofthe opecode. At the fields following the field of the operand [0], thereare located data for identifying a descriptor. Type of data to be read,data length and address and the like are located at specific operands.

When data is written in the descriptor which is set to the accessiblestate by the open descriptor command shown in FIG. 29, necessary data iswritten in the descriptor by transmitting a write command. FIG. 31 showsan arrangement of this write command. The arrangement of the writecommand will be described. A value corresponding to a write descriptorcommand is located at the field of the opecode, data for identifyingdescriptor is located at the field of the operand [0] and a subfunction,a group tag, a write data length, an address, an original data lengthobtained before data is rewritten and write data are allocated at thefollowing operands. As the subfunction, there is provided a subfunctionfor instructing a partial rewriting.

When the access to the corresponding descriptor is ended after data hasbeen read out from the descriptor by the read command shown in FIG. 30or data has been written in the descriptor by the write command shown inFIG. 31, the access to the corresponding descriptor is ended bytransmitting a close command. The close command can instruct the closeby a subfunction using a command having an arrangement similar to thatof the open command. Specifically, as shown in FIG. 32, a valuecorresponding to an open descriptor command is located at the field ofthe opecode, a value of a descriptor type to be opened is located at thefield of the operand [0], a value of a list ID to be opened is locatedat the fields of the operands [1], [2], and a value of a subfunctionindicating the close is located at the field of the operand [3]. Fieldsfollowing the field of the operand [4] are reserved.

Next, the manner in which the board shown by the BBSID of FIG. 21 isread out from the controller of another device on the bus line by usingthe AV/C command will be described with reference to flowcharts of FIGS.24 to 27.

Referring initially to the flowchart of FIG. 24, the SID (subunitidentifier descriptor) of the BB subunit (bulletin board subunit) is setto the read enable state by transmitting the read open command (stepS11). In this state, the SID of the BB subunit is designated and thecontents of the SID are read out by the read descriptor command. Then,the size of the list ID and the board type supported by the BB subunitof the target are obtained (step S12). Thereafter, the SID of the BBsubunit is closed (step S13).

Next, an arbitrary list ID is designated from the root list ID shown bythe SID and the list is set to the read enable state by transmitting theread open command. (step S14). It is determined based on the attributedata whether or not the object within the list has an ID (step S15).Further, it is determined whether the list type is of the write enablelist type or not (step 516). If the list type is of the write enablelist type, then a limit required when the entry is written is detected(step 17). If it is determined at the step S16 that the list type is notthe write enable list type, then the limit required when the entry iswritten is detected at the step S17 and then it is determined whether ornot the list type is of the board list type (step S18).

If it is determined at the step S18 that the list type is of the boardlist type, then control goes to the flowchart of FIG. 25 which isprocessing for reading out a board list entry. In this processing, thetotal number of entries within the corresponding descriptor is detectedfrom data indicative of the number of the object entries of thecorresponding board list entry, and a counter set within the controlleris initialized (step S21).

Then, it is determined whether or not the total number of entries isgreater than the count value of the counter (step S22). In the initialstate, the total number of the entries becomes greater than the countvalue of the counter. If it is determined that the total number of theentries is greater than the count value of the counter, then it isdetermined whether or not the child list ID of the attribute within theobject is 1 (i.e., whether or not the child list exists) (step S23). Ifit is determined that the child list ID is 1, then the child list ID isread out (step S24). If it is determined at the step S23 that thereexists no child list, then after the child list ID has been read out atthe step S24, information of the entry (entry specific information) isread out (step S25), the counter value is incremented in an ascendingorder (step S26) and control goes to the judgment at the step S22.

If it is determined at the step S22 that the total number of the entriesis equal to the count value of the counter, then the reading is ended bytransmitting a board list closing command (step S27).

If it is determined at the step S18 of the flowchart shown in FIG. 24that the list type is not of the board list type (i.e., it is determinedthat the list type is of the information list type), control goes to aflowchart of FIG. 26 which is processing for reading an information listentry. The total number of the entries within the correspondingdescriptor is detected from data indicative of the number of the objectentries of the corresponding information list, and a counter set withinthe controller is initialized,(step S31).

Then, it is determined whether or not the total number of the entries isgreater than the count value of the counter (step S32). In the initialstate, the total number of the entries becomes greater than the countvalue of the counter. If it is determined that the total number of theentries is greater than the count value of the counter, then an objectID is read out (step S33). Further, it is determined whether or not thechild list ID of the attribute within the object is (i.e, whether or notthere exists the child, list) (step S34). If it is determined that thechild list ID is 1, then the child list ID is read out (step S35). If itis determined at the step S34 that there exists no child list, thenafter the child list ID has been read out at the step 535, informationof the entry (entry specific information) is read out (step S36), thevalue of the counter is incremented in an ascending order (step S37),and control goes back to the judgment at the step S32.

If it is determined at the step S32 that the total number of the entriesis equal to the count value of the counter, then the reading is ended bytransmitting a command for closing this information list (step S38).

Next, the manner in which the information child list is read out when itis determined that the information list includes the child list will bedescribed with reference to a flowchart of FIG. 27.

First, the child list ID read out from the information list at the stepS35 is designated, and the information list is set to the read enablestate by transmitting the read open command (step S41). In this state,it is determined whether or not the list type is of the write enablelist type (step S42). If it is determined that the list type is of thewrite enable list type, then a limit required when data is written inthe entry is detected (step S43). If it is determined at the step S42that the list type is not of the write enable list type, then after thelimit required when data is written in the entry has been detected atthe step 43, it is detected based on the attribute whether the entrywithin the list includes an object ID (step S44). Then, the total numberof the entries is judged from the number of the object entries, and thecounter is initialized (step S45).

Then, it is determined whether or not the total number of the entries isgreater than the count value of the counter (step S46). In the initialstate, the total number of the entries becomes greater than the countvalue of the counter. If it is determined that the total number of theentries is greater, then it is determined whether or not the entryincludes the object ID (step S47). If it is determined that the entryincludes the object ID , then the object ID is read out from the entry(step S48). Further, it is determined whether or not the child list IDof the attribute within the object is 1, (i.e., whether or not the entryincludes the child list) (step S49). If it is determined that the childlist ID is 1, then the child list ID is read out (step 550). Then, entryinformation (entry specific information) is read out (step S51), thevalue of the counter is incremented in an ascending order (step S52),and control goes back to the judgment at the step S46.

If it is determined at the step S46 that the total number of the entriesis equal to the count value of the counter, then the reading is ended bytransmitting a command for closing this information list (step S53).

While the descriptor read processing has been described so far withreference to the flowcharts of FIGS 24 to 27, data can be written in thewrite enable descriptor by issuing the write command while designatingthe position of the list by a procedure similar to that of the readprocessing.

Since the bulletin board subunit is prepared in one device connected viathe bus line of the IEEE 1394 system, the descriptor making the subunitis formed in the hierarchical structure and each board and informationcan be judged from the highest-order descriptor, the devices connectedvia the busline can efficiently share data written in the bulletin boardsubunit and control can be made.

As shown in FIG. 2, for example, if the bulletin board subunit (BBS) 4is prepared on the DVCR 200 side, the BBS controller 5 within the IRD100 connected to the DVCR 200 via the bus line 1 can read out the BBS 4in the procedure according to the flowcharts of FIGS. 24 to 27 and canjudge the situation in which the timer-activated recording is set in theDVCR 200. When the tuner within the IRD 100 needs the reception for thetimer-activated recording, for example, corresponding operation isexecuted by reading this BBS 4.

Since fundamental information such as the start time of thetimer-activated recording is directly written in the resource scheduleboard directly instructed by the root list ID within the BBSID which isthe highest-order descriptor, the above information can be obtainedrapidly.

Since information accompanying with the timer-activated recording, forexample, is written in the information list descriptor, the detailsconcerning the timer-activated recording can be known by reading outinformation from the respective information list descriptors. Forexample, the details such as a title and contents of a timer-activatedrecording program can be known. Information such as the title and thecontents of the program can be obtained by using data called an EPG(electronic program guide) superimposed upon broadcasting data when thedata is a digital broadcasting received by the IRD 100, for example.Since the object IDs are set to information set in the respectivedescriptors and the respective resource schedule boards, it becomespossible to easily understand a correspondence between the respectiveinformation.

A new timer-activated recording can be set by writing data in the BBS 4under control of the controller 5 within the IRD 100. In this case, datais written in the write enable descriptor. In that case, wheninformation of a capacity in which data can be written is read out fromthe descriptor, and judged, a capacity in which data can be written canbe judged, and hence the setting for writing can be executed properly.

Further, since the descriptor set within the BBS is limited in writing,if detailed information concerning the timer-activated recording setwithin the DVCR 200, for example, is prepared on the descriptor in whichthe writing was limited, then the timer-activated recording cannot becorrected by the controller 5 within the IRD 100, and hence thetimer-activated recording can be protected accurately.

The present invention is not limited to the above embodiment and can bevariously modified without departing from the gist of the presentinvention.

For example, while the BBS (bulletin board subunit) is used to writeinformation concerning the timer-activated recording as set forth in theabove embodiment, the present invention is not limited thereto and otherdata that should be opened through the bus line may be written in adescriptor having a similar hierarchical structure by the BBS. Devicesusing the BBS can be applied to electronic device other than the aboveIRD and DVCR (various video devices, audio devices, etc.).

Furthermore, while the bus line for connecting the devices is applied tothe bus line of the IEEE 1394 system in the above embodiment, thepresent invention is not limited thereto and bus lines of otherstandards may be used. In this case, in addition to bus lines connectedvia cables, a radio transmission line for similarly transmitting data bya radio communication among a plurality of devices can be applied to thepresent invention.

1-12. (canceled)
 13. An information processing system for transmittinginformation among a plurality of audiovisual apparatuses connectedthrough an IEEE 1394 network, comprising a first audiovisual apparatusconnected to said IEEE 1394 network that includes an information openingdata storage section for opening predetermined information toaudiovisual apparatuses connected through said IEEE 1394 network and acontrol section for reading or writing data stored in said informationopening data storage section by receiving predetermined commands throughsaid IEEE 1394 network, and a second audiovisual apparatus connected tosaid IEEE 1394 network that includes a control section for issuingcommands for instructing the reading or the writing of data stored insaid information opening data storage section, wherein data is stored insaid information opening data storage section provided in said firstaudiovisual apparatus in the descriptor format having a predeterminedhierarchical structure, said predetermined information is stored in abroad set in said descriptor format, the position at which saidpredetermined board is stored is directly instructed by a highest-orderdescriptor having said hierarchical structure, and informationconcerning said predetermined information is stored in an informationarea instructed when said hierarchical structure is retrieved from saidhighest-order descriptor.
 14. An information processing system accordingto claim 13, wherein said information area within said informationopening data storage section of said first audiovisual apparatusincludes an area in which information from said second audiovisualapparatus can be written and an area in which the writing of informationfrom said second audiovisual apparatus is limited.
 15. An informationprocessing system according to claim 14, wherein when an area in whichinformation can be written is set as said information area, a storagearea of information concerning a capacity in which information can bewritten is added to a descriptor, and the capacity in which informationcan be written is judged by the control section of said secondaudiovisual apparatus.
 16. An information processing system according toclaim 13, wherein IDs are added to respective information stored in apredetermined board within the information opening data storage sectionof said first audiovisual apparatus, a common ID is added to respectiveinformation stored in said information area, and the control section ofsaid second audiovisual apparatus judges based on said ID acorrespondence between information stored in said board and informationstored in said information area.